Such spacers and corresponding devices are known, for example, from DE-PS 25 21 855. In this patent specification a device for inserting intermediate members between two intersecting strings of a set of tennis racket strings is described, the intermediate members being formed as guide cross-pieces (cross-blocks) with pairs of arms running at right angles to one another and partly embracing the strings, and the body of the device holding a supply magazine for the intermediate members, having a handle and having fork-shaped prongs arranged at its front end to force the intersecting strings apart.
The distinctive feature of this device is said to be that the supply magazine is connected with a position between the prongs via a positioning device for the intermediate members and a guide passage, and that a means for delivering the members, through which means the last section of the guide passage adjacent to the prongs runs, is linked pivotably to the body of the device next to the prongs, and is traversed by a slit crossing the last section, into which a tongue rigidly connected to the device body projects so that the last section of the guide passage is blocked or free depending on the position in which the delivery means is pivoted.
It is a disadvantage of this device that the guide cross pieces must be specifically arranged before they can slide into the delivery passage. It is not unusual for individual cross-pieces to jam so that simply slipping into the delivery passage becomes impossible. In addition the construction of the device is very difficult and thus also very dear.
Another form, which is an improvement on the solution described in DE-PS 25 21 855, is known from DE-OS 33 29 150.
In the device described in this published specification discs, preferably annular-shaped, are pushed out of a storage container by means of a pusher housed in a delivery passage, the operating part of which extends through the cover, and between two strings that are forced apart by prong-like projections of the device.
In doing this, care must always be taken that there is only one disc in the delivery passage, as otherwise a blockage, i.e. wedging of the discs, can occur. For more reliable transport of the discs it is necessary to push the pusher right back after each operation of the lever action, so that a new disc can slide down. To provide the normal striking area of a tennis racket with spacers, about 120 discs must be pushed between the strings. This manipulation requires a relatively large amount of effort and the device and its assembly are inconvenient.